Substation rectification of carrier telegraph currents



Oct. 28, 1930. L. c.- ROBERTS suBs'rATIoN RECTIF'IGATION QF CARRIER TELEGRAPH CURRENTS Filed .July 9. 1928 Patented Oct. 28, 1930 Y j A i 1,779,495

VeerEN'r OFFICE j LELAN D C.

ROBERTS, 0F TOWACOQNEW JERSEY, ASSIGNOR T0 AMERCAN'TELEPHONE AIND TELEGRAPH COMPANY, A CORPOBATION 0F NEW YORK sUBST-VI'IONy RECTIEIGATIoNor -CARREER TELEGRAPH CURRENTS i Application inea July 9, 192s. sen-.a1 No. 291,118.v

This invention'relates tothe art of telegraph communication and discloses an improved system for carrier current telegraphy whereby rectification of the, carrier current 5 is accomplished at the subscribers station instead of at the central oiiice. The use of the improved method thus eliminates the neces-V sity for mechanical repeaters at the central oflice to repeat signals over the loop circuitJ 'p to the telegraph sounder at the suloscribers` station.

ln carrier current telegraph systems in general, each telegraph station is connected to a local central office over a loop circuit. Distant stations are connected over a trunk circuit extending between the respective central oftices. The carrier current is transmitted over the trunk circuit only, thesignaling between a central oflice and theVv local station being laccomplished by direct current telegraph means operating'over the loop circuit.

The carrier current is thus rectified lat thel central office and caused to operate a mechanical repeater which repeats the signals to the telegraphsounder at the local station.

' With a system whereby the carrier current is Vtransmitted frlomjthecentral office at the sending end through the central oiice at the receiving end and directly to the 'local telegraph station there, the mechanical repeater equipment could be eliminated from the central offices ata considerable economy. Rectificati'onlot the carrier currents in such a system would be accomplished at the telegraph station, and the rectified currents caused to operate a telegraph sounder through the medium of suitable relay means located there. V'The present invention discloses a system of this type which is best explained in detail by'reference tothe drawing, which showsin schematic form one channel of a. carrier telegraph system embodying the invention.

The `drawing discloses a so-called fourwire"7 trunklcircuit consisting of circuits 1 and 2 extending between central oiices C and D distant from each other; Circuit 1 trans- `mits 'in the*` direction from right to'left on the drawing, while circuit2 transmits from leftto right. Subscribers [telegraph station Ar is connected to trunk circuits 1 and 2 over or full wave rectification.

loops V32 and 3, respectively. Similarly station B is connected to the opposite ends of trunks 1 and 2 over loops 4 and 5, respectively. The Aequipment at station A comprises polar relays 14 and 16, rectifying means 1.3 and 17, Vvariable resistance 24, a sendingkey 11 and a telegraph sounder 31 connected, as shown. Similar equipment connected in a corresponding manner is shown at station B.

Key 11 is connected in series with loop 3 and controls a source of oscillating current 12 also connected in series with loop 8 at central oflice C. VVithkey 11 depressed, as

shown, current from source 12 is transmitted to stations A and B by means oftransformer 26. At station A, this currentl is applied to the circuitv containing rectifying means 13 by Vmeans of transformer 27. Anytype of rectifying device may be used for eitherhalf It issuggested, however, that the recently developed copper oxide rectifier is best adapted for this purpose since it is compact, economical and requires no attention after installation. vThe rectifying means v13 causes a fluctuating direct currentto flow through the line'winding of. polar relay 14. This winding is so pole'd that the rectilied current causes the armature of the relay tomove against-its marking contact M. Ina similar manner,-

current from source 12 is rectified by device 18 at station B, causingrectiled current to flow through the line winding of polar relay 19, thus-holding the armature of this relay i against its marking contact M.

With relay 14 thus in its marking position, current from battery 15 flows'through the armature of relay 14, through the telegraph sounder 31, and the armature of rela 16, which as explained below,is normally a so in its marking position, to 'ground at 28. This current holds sounder 31 also in its marking position. In a similar manner, current from battery 23 through sounder 30 to` ground at 29, holds the sounder at station B in-its marking position.

When key 11 is released, it opens `the series circuit containingthe carrier current 12 and prevents the further transmission thereof to the subscribers stations. Immediatelythereupon, the armatures of relays 14 and 19 are caused to move against their spacing contacts S. This is accomplished through electrical biasing means. t Will be noted that at station A, current from battery 15 flows continuouslythrough the auxiliary Winding of relay 14, through resistance 24 and the auxiliary Winding of relay 1G, to ground. This current is such that it tends to move the armatures of both said relays against their spacingv contacts. -Tlie current is adjusted by means of variable resistance Q4 so that with rectified current in the line Winding of the relay operative, the relay Vis held against its marking contact, but with no current flowing in the line iinding, the biasing current holds the armature against the spacing contact.

lVhen relay 14C thus moves against its spacing contact upon release of key 11, it opens the direct current path from battery 15, through sounder 31 causing the latter also to move against its spacing contact with the customlary click. Similarly, at station B, sounder 30 finoves against its spacing contact with a click. It will be seen, therefore, that sounders 31 and 30 follow the operations of the sending key 11 in `accordance with the signals transmittedl Polar relays 16 and 21 are controlled by sending ltey 9.2, through the medium of the oscillator 33 locatedat central ofiice D. While no" signals are being transmitted key 22, as Well as hey 11, is normally closed. The operation of ,key 22 operates relays 16 and 21 in theV manner described above in connection ywith transmission from station A. The

operation of these relays alternately opens and closes, at the respective relay contacts,

"the circuits containing sounders 30 and 81,

thus causing the sounders to operate in aecordance. with the signals transmitted from stition B.

If duringpthe transmission of signals, say from station A, the operator at station B Wishes to `interrupt or .brealr the message, heinierely openskey 22. rI his causes relay 16 at station Ato move against its spacing contact, opening the circuit containing sounder B1. The operator at station A, upon noting that sounder 31 no longer follows the operations ot key 11, is thus made aware of the brealr.

Stations A and B, of course, constitute only one' of a plurality of distinct channels operating over the trunk circuits 1 and 2. v@ther channels identical in Wiring Withstatiou A, Aare connected to Vleads 4(A3 and 8ivhile at the distant end, stations similar tostation B are connected to leadsv 7 andt).

channel xoperates"on a carrier frequency distinct from the othe'rjeliannel and `filters 1,0 are inserted in each channelto pre- Vvent interference between channels,

i dlvllat is claimed ,isz i' uIn canriler telegraplnsystenicomprising a line extending from a first subscribers station through al certain point to a second subscriber-s station, and having associated therewith at said point a source of carrier current, with control means at said first station for controlling the same, the method of signaling which consists in operating said control means, causing the resultant pulses ot' carrier current to be transmitted to both said stations, recti'fying the received pulses Yof carrier current at said stations, utilizing the pulses of rectified current for signaling.

Q. In a carrier telegraph system comprising a line extending from a first subscribers station through an intermediate office to a second subscribers station, and having associated therewith at said office a source of carrier current, the method of signaling which consists in controlling from said first station the output of said carrier current source, transmitting the resultant pulses of carrier current to both said stations, rectifying said currents thereat, and utilizing the rectified currents for signaling.

3. In a carrier telegraph system comprisr. lng a line extending from a first subscribers station through intermediate offices to a second subscribers station, `and having associated therewith at the office yadjacent each said station a. source of carrier current, the.

method 4of signaling which consists in. controlling the output of either carrier current source from the station adjacent thereto,

transmitting the resultant current aulses v t,

from a given source to both stations, rectifying said current pulses at said stations, and utilizing. said rectified currents for signaling thereat.

4. A carrier telegraph system comprising a sending and a receiving subscribers stationa line` connecting said stations through intermediate,oflices,a source of carrier current at the office adjacent the sending station, control means at ,the sending station for transmitting pulses of said current to both stations, means at said stations for rectifying said current pulses, and telegraph sounder means thereatV operable in accordance With 4said pulses of rectified current.

5. A carrier telegraph system comprising tivo subscribers stations, a pair of oppositely transmitting lines connecting the saine through intermediate offices, a source of carrier current atthe office adjacent each station associated With the line transmitting therefronncontrol means ateach station ,for transinitting'pulses of carrier current from the adjacent ofiice to both stations over the circuit transmitting.therefrom, means at each 'station individual to said lines for rectifying received pulses of carrier current, means `to operate a sounder at each station in accordance with said pulses` of rectified lcurrent received over either line.

6. Aj Y,carrier telegraph-system;comprising a pair of subscribers telegraph stations connected by a line extending through intermediate oiiices, a source of carrier current at the office adj acent each station, control means at each station for causing the transmission of carrier current pulses to both stations from the adjacent oflice, means at each station for rectifying said current pulses, telegraph sounder means at each station operable in accordance with said pulses of rectified current.

7. A carrier telegraph system comprising a line extending between two subscriberssta? tions through intermediate offices, a source'of carrier current at the otiice adjacent each station,control means at each station for causing the transmission of carrier current pulses from said adjacent oflice to the distant station, means at each station to rectify received pulses of carrier current, telegraph sounder means at each station operable in accordance with said pulses of rectified current.

8. A carrier telegraph system comprising two subscribers stations, a pair of oppositely transmitting lines connecting the same through intermediate oices, a source of carrier current at the office adjacent each station associated with the line transmitting therefrom, control means at each station for transmitting pulses of carrier current from the adjacent otlice to both stations over the circuit transmitting therefrom, means at each station individual to said lines for rectifying received pulses orf carrier current, means to operate a sounder at each station in accordance with said pulses of rectified current received over either line, means for either station to transmit a break signal tothe distant station while said distant station is sending.

9. A carrier telegraph system comprising a pair of subscribers telegraph stations con-V nected by a line extending through intermediate ofices, a source of carrier current at the office adjacent each station, control means at each station for causing the transmission of carrier current pulses to both stations from the adjacent office, means at each station for rectifying said current pulses,

Vtelegraph sounder means at each station operable in accordance with said pulses ofV rectified current, means for either station to transmit a break signal to the distant station I r while said distant station is sending.

10. In a carrier telegraph system in combination, a line extending from a first Vsubscribers station through intermediate offices to a second subscribers station and having associated therewith at the ofice adjacent each said station a source of carrier current, control means atV each station for causing pulses of carrier current from the source at the adjacent oiiice to be transmitted to' both stations in accordance with the operation thereof, means at each office to rectify received pulses of said carrier current, a telegraph sounder at each office, means at each olice to operate said Sounders in accordance with the pulses of rectifiedl current.

, ll.l A carrier telegraphsystem comprising a sending and a receiving subscribers station, a line connecting said stations'through intermediate offices, a source of carrier current at the office adjacent the sending station, control means at the sending station for transmitting pulses of said current to bothstations, copper oxide rectifying means at said stations for rectifying said current pulses, and telegraph sounder means thereat operable in accordance with* said pulses of rectified current.

In testimony whereof, I have signed my name to this specification this 6th day of J uiy, 1928.

LELAND G. ROBERTS. 

